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Old 10th Aug 2005, 3:54 pm   #3
Station X
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Location: Ipswich, Suffolk, IP4, UK.
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Default Re: Vintage radio safety

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I was under the impression that this website was to give help to restoring vintage radio equipment.However,seeing some of the content recently,this seems to be not the case.especially when it comes to electrical safety.
Surely if you're restoring a Vintage Radio or anything else for that matter you should make sure it's safe? Are you saying that giving safety advice is unhelpful?

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Set manufacturers go to a lot of trouble to ensure their products are safe,they have to comply with BSI,and IEE regulations,which were rigoursly enforced,these safety requirements far exceed present day standards,so any modification or "updating"will generally impair safety.
You've got your tenses mixed up here. I think you're saying that vintage sets were manufactured to comply with the standards of the day. You go on to say that these standards "far exceeded" present day standards. Have you actually sat down and studied the old and new standards side by side to prove this? In my experience safety standards and legislation get tougher and more rigidly enforced. Not the other way round.

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A large part of Britain had DC mains,this is why electrical safety was so important.A lot of sets had the BS 5a connector,similar to a shaver plug,these were known as a safety connector,since you could not take the back cover off without withdrawing the connector.Another reason was to reverse polarity,this was important when using 3 pin sockets since the red wire went to the right hand pin which is the "live".However this could be negative or postive depending on which main you were connected to,which varied from house to house.The 2pin connector facilitated an easy transpose.
Interesting historical information, but not relevant today when there are no DC mains.

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On AC there is no polarity to ensure,although less hum may occur when the chassis is connected to neutral.
On radios with single pole mains switching the switch should be connected in the live wire so that the set will not be live when switched off. Similarly any exposed voltage adjustment terminals should be in the neutral wire. Reversed mains polarity will defeat this.

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Another reason for the existance for the connector is to quickly isolate the set,this regulation applies today,and is seen on most appliances that are not hand held or fixed,todays connector is generally the flimsy IEC pattern made of plastic .
What exactly do you mean by an appliance that is not hand held or fixed? Anything small can be held in the hand. PORTABLE radios for example can be handheld and they do have a 2 pin mains connector. I have checked a few of these plugs on my own appliances and they are far from flimsy. I COULD hit them with a hammer and not smash them. An old plug made from hard plastic can be smashed just by dropping it on the floor.

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Any attempt to break the earth,(ie an isolating transformer)can be very dangerous.
Isolating transformers are only intended to be used when working on a live set. Not when it is in everyday use. If you touch the live side of the mains when in contact with earth you won't get a shock if you're using an isolation transformer.

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Most AC only sets used a similar transformer,and one would rightly assume that the chassis needs an earth for safety,yet most mains leads were two core only,now do you update and fit a 3 core lead?If you did, it may be safer,but radio equipment does not like to be earthed to a mains earth since this is a poor rf earth and may introduce a lot of noise into the rf stages,also if someone connected the earth socket to a ground spike as intended,this would then be multiple earthing and could bring another hazard if an ELCB is used,also there would be loop currents between the two earths,which would mean further noise at least.
I agree that providing a protective mains earth may lead to an increase in noise. However safety is more important. If you or I found ourselves in court because someone killed or injured themselves using a set we'd restored the excuse "providing a protective earth would have increased noise" would cut no ice at all.

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However all this seems uneccessary,if the insulation is tested with a megger ,and a good reading is obtained,then there should not be a need for earth
What tests good today can go faulty tomorrow. My car had perfect brakes when it came out of the factory, but I still have to get them inspected and tested every year at MOT time.

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Vintage radio sets are safer than a lot of present day equipment.
Such as?

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A lot of manufacturers did not fit fuses in the supply lead,this is bad,in this case make sure you have a 2A fuse in the plug.
As far as I know, and I haven't checked, the UK is the only country that uses fuses in mains plugs. This is an excellent safety feature brought about by upgrading of old standards. Unfortunately these have been misnamed as "13 Amp Plugs", so everyone seems to think they need a 13 amp fuse! However I would fit a 1 amp fuse where available.

Graham.

Last edited by Station X; 10th Aug 2005 at 4:37 pm.
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